Refrigerating cycle

ABSTRACT

The freezing cycle according to the present invention is provided with a first means for safety that leaks the high pressure to the low-pressure side when the high pressure reaches a level equal to or higher than a first specific pressure, a second means for safety that releases the high pressure into the atmosphere when the high pressure reaches a level equal to or higher than a second specific pressure, a third means for safety that stops the operation of the compressor when the high pressure reaches a level equal to or lower than a third specific pressure and a fourth means for safety that releases the low-pressure into the atmosphere when the low-pressure reaches a level equal to or higher than a specific pressure. In addition, a splash-preventing film is formed over specific areas of devices constituting the freezing cycle.

TECHNICAL FIELD

The present invention relates to a freezing cycle used in anair-conditioning system for vehicles, and in more specific terms, itrelates to a freezing cycle having a safety device that protectscomponents constituting the freezing cycle from damage caused by anabnormally high pressure when carbon dioxide is used as a coolant.

BACKGROUND ART

Examples of freezing cycles in the prior art include the one disclosedin Japanese Unexamined Patent Publication No. H 7-25231. This freezingcycle, which uses a freon coolant, comprises, at least, a compressorwhich compresses the coolant, and a condenser, an expansion valve and anevaporator which are connected to the compressor in series. The freezingcycle is further provided with an auxiliary coolant passage set parallelto the expansion valve and a valve for opening/closing the auxiliarycoolant passage, and the auxiliary coolant passage is opened when thelow-level pressure becomes equal to or lower than a specific value.

In this example, by allowing the high pressure to bypass the expansionvalve to directly flow into the low-pressure side and by thus preventinglow-pressure from becoming reduced, increases in the pressure and thecompression temperature at the outlet side of the compressor areprevented.

In addition, there are freezing cycles provided with a device forturning off the cycle by judging that the quantity of the coolant is notsufficient or that the load is too low due to a low external airtemperature when the high pressure becomes equal to or lower than aspecific value, i.e., freezing cycles provided with a low-level cutswitch.

Other safety mechanisms that may be provided in freezing cycles includea device that stops the operation of the compressor when the highpressure becomes equal to or higher than a specific value, a device thatstops the compressor when the outlet temperature at the compressorbecomes equal to or higher than a specific value, a device thatdischarges the high-pressure coolant into the atmosphere when the highpressure becomes equal to or higher than a specific value and a fusibleplug that allows the coolant to be discharged into the atmosphere whenthe coolant temperature becomes equal to or higher than a specificvalue.

However, while extensive research has been conducted into substancesother than freon, such as carbon dioxide (CO₂), to be used as a coolantin the freezing cycle in air-conditioning systems for vehicles toaddress the global environment issue, a freezing cycle using carbondioxide, which has a low critical point of approximately 31.1° C. as thecoolant constitutes a reciprocal critical cycle that crosses over thecritical point and, as a result, the high pressure in such a freezingcycle is as high as 10 times the high pressure of the freon coolant.Since this pressure level is close to the limit of tolerance ofaluminum, it has become more crucial to provide an effective safetydevice for cycle protection than in a freezing cycle in the prior artthat uses a freon coolant (conventional cycle) when designing a heatexchanger or the like by taking into consideration the safety factor.

In more specific terms, since the normal operating pressure on the highpressure side is approximately 10˜15 MPa and the coolant does not crossover the critical point to become condensed in the reciprocal criticalcycle, the high level side pressure reacts more sharply to fluctuationsin the load compared to a freon coolant which becomes condensed on thehigh pressure side. Thus, it is understood that the likelihood of thehigh pressure in a reciprocal critical cycle reaching the vicinity ofthe maximum normal operating pressure is much higher than the likelihoodof that occurring in the cycles currently in use. If a high-pressure cutswitch is employed in a reciprocal critical cycle, a problem will occurin that the high-pressure cut switch will be activated too frequently.It is to be noted that the high pressure in the conventional cycle isapproximately 1.2˜3 MPa, with the setting for the high pressure cutswitch at approximately 3 MPa.

In addition, since the critical point of the coolant is low in thereciprocal critical cycle, the balance pressure between thehigh-pressure side and the low-pressure side in the reciprocal criticalcycle left in hot daylight becomes as high as approximately 10 MPa.While it is desirable to minimize the coolant volume on thehigh-pressure side in order to prevent the balance pressure from rising,there is a problem in that minimizing the coolant volume on thehigh-pressure side would increase the passage resistance on thehigh-pressure side to result in a large pressure loss.

Thus, when using carbon dioxide as an alternative coolant to freon, itis necessary to take safety measures to prevent damage to variouscomponents which would be caused by the high pressure while taking intoconsideration the eventuality of such damage occurring.

Accordingly, an object of the present invention is to provide a freezingcycle having a means for safety that is most suited for application in afreezing cycle using carbon dioxide as a coolant.

DISCLOSURE OF THE INVENTION

The freezing cycle according to the present invention, which uses carbondioxide for a coolant and comprises, at least, a compressor thatcompresses the coolant to a level in a super critical range, a radiatorthat cools the compressed coolant, an expansion device that lowers thepressure of the cooled coolant down to a gas/liquid mixed range and anevaporator that evaporates a liquid-phase coolant generated by theexpansion device, having a high-pressure line extending from the outletside of the compressor to the intake side of the expansion device and alow-pressure line extending from the outlet side of the expansion valveto the intake side of the compressor, is further provided with a firstmeans for safety that communicates between the high-pressure line andthe low-pressure line when the pressure in the high-pressure linebecomes equal to or higher than a first specific pressure, a secondmeans for safety that communicates between the high-pressure line andthe atmosphere when the pressure in the high-pressure line becomes equalto or higher than a second specific pressure higher than the firstspecific pressure, a third means for safety that stops the drive of thecompressor when the pressure in the high-pressure line becomes equal toor lower than a third specific pressure and a fourth means for safetythat communicates between the low-pressure line and the atmosphere whenthe pressure in the low-pressure line becomes equal to or higher than afourth specific pressure higher than the third specific pressure.

In addition, it is desirable to constitute the first means for safetywith a high-pressure relief valve that releases the high pressure towardthe low-pressure side when the high pressure reaches the first specificpressure. Furthermore, in consideration of the pressure loss in thehigh-pressure line occurring as a result of minimizing the high-pressureside coolant volume to lower the balance pressure when the vehicle isleft in the hot sun, the high-pressure relief valve should communicatebetween the area near the outlet side of the compressor and the area inthe vicinity of the intake side of the compressor.

In consideration of the tendency of carbon dioxide to leak easily, it ismore desirable to assume a structure that ruptures at a preset pressurelevel rather than a valve structure in the second means for safety, andmore specifically, it is desirable to constitute the second means forsafety with a high-pressure rupture disk that ruptures at the secondspecific pressure higher than the first specific pressure.

The third means for safety, which is provided to protect the compressorfrom any damage that may otherwise occur when the coolant leaks, stopsthe compressor when the pressure in the high-pressure line becomes equalto or lower than the third specific pressure. More specifically, it isprovided with a pressure sensor that detects the high pressure, andstops the means for driving the compressor when the level of thepressure detected by the pressure sensor is equal to or lower than thethird specific pressure (by shutting down the electromagnetic clutchlinking the compressor to the engine, stopping the motor, etc.).

It is desirable to constitute the fourth means for safety with alow-pressure rupture disk which ruptures when the pressure in thelow-pressure line is at the fourth specific pressure level higher thanthe third specific pressure. Since the pressure in the low-pressure linerises as the temperature increases in the event of a fire occurring inthe engine room, the low-pressure rupture disk will fulfill a functionsimilar to that of a fusible plug in the prior art. In addition, sinceit achieves a pressure-dependent function, it prevents damage occurringwhen the coolant is charged to an excessive degree by mistake.Furthermore, it is capable of tolerating an abnormal increase in thebalance pressure occurring when the vehicle is left in the hot sun.

Alternatively, a safety device comprising a relief valve constitutingthe first means for safety, a high-pressure rupture disk constitutingthe second means for safety and a low-pressure rupture disk constitutingthe fourth means for safety provided as an integrated unit, may becreated to be installed as an integrated part of the compressor.

In addition, in order to further improve the safety of the freezingcycle, a splash-preventing film should be formed over the areas whererupture may occur due to a high pressure, such as the header tank of theradiator, the accumulator main unit, the hose caulking metal fixturesand the evaporator tank. It is desirable to constitute thesplash-preventing film by using PET (polyethylene terephthalate) are PVB(polyvinyl butyryl) to form a base member with an adhesive layer formedon the surface of the base member. Alternatively, a laminated sheetconstituted by enclosing a fibrous substance or a fibrous sheetconstituted of resin or metal in the base member may be used instead.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of the reciprocal critical cycleaccording to the present invention;

FIG. 2 is an enlarged sectional view of a portion of an embodimenthaving a safety device mounted at the compressor;

FIG. 3 is an enlarged sectional view of a portion of another embodimentof the safety device; and

FIGS. 4(a) and 4(b) each present an enlarged sectional view of a portionof a splash-preventing film.

THE BEST MODE FOR CARRYING OUT THE INVENTION

A Freezing cycle 1 in FIG. 1, which uses carbon dioxide as a coolant, isprovided with a compressor 3 driven by the engine (not shown) via anelectromagnetic clutch 2 linking them. A radiator (gas cooler) 4 thatcools the coolant that has been compressed by the compressor 3 to alevel in a super critical range is connected to the outlet side of thecompressor 3. Since the coolant is in the super critical range, thecoolant remains a gas-phase coolant even when it has been cooled in thegas cooler 4 and, thus, the gas-phase coolant flows into a first heatexchanging unit 6 constituting an internal heat exchanger 5 at the nextstage. The gas-phase coolant flowing through the first heat exchangingunit 6 in the internal heat exchanger 5 becomes further cooled through aheat exchange with the low-pressure, low-temperature gas-phase coolantpassing through a second heat exchanging unit 7 of the internal heatexchanger 5, which is to be detailed below, to be delivered to anexpansion device 8. The expansion device 8 lowers the pressure of thehigh-pressure gas-phase coolant down to a gas/liquid mixed range, and isconstituted as a type of automatic expansion valve. The coolant in thegas/liquid mixed state resulting from the pressure reduction at theexpansion device 8 absorbs heat at an evaporator 9 provided on thedownstream side relative to the expansion device 8 and evaporates tobecome a gas-phase coolant.

An accumulator 10 is provided on the downstream side relative to theevaporator 9. At the accumulator 10, the quantity of the coolant flowingthrough the entire freezing cycle is adjusted and gas/liquid separationis achieved. The coolant having undergone the gas/liquid separation isthen delivered to the second heat exchanging unit 7 of the internal heatexchanger 5 mentioned earlier. The coolant delivered from theaccumulator 10 to the second heat exchanging unit 7 then undergoes heatexchange with the gas-phase coolant passing through the first heatexchanging unit 6 to become heated and is taken into the compressor 3.Thus, the freezing cycle 1, which absorbs heat at the evaporator 9 andradiates heat at the gas cooler 4, is achieved.

It is to be noted that in this freezing cycle 1, the range extendingfrom the outlet side of the compressor 3 to the intake side of theexpansion device 8 is defined as a high-pressure line 11 and the rangeextending from the outlet side of the expansion device 8 to the intakeside of the compressor 3 is defined as a low-pressure line 12.

While the normal operating pressure in the high-pressure line 11 isapproximately 10˜15 MPa in the freezing cycle 1 structured as describedabove, the pressure tolerance of the gas cooler 4 constituted of analuminum material, in particular, is 20 MPa at the most under normalcircumstances due to such factors as the heat exchanging rate, theweight and the cost that must be taken into consideration, and thus, itis necessary to take safety measures to protect the freezing cycle.Accordingly, according to the present invention, a bypass passage 13communicating between the high-pressure line 11 in the vicinity of theoutlet side of the compressor 3 and the low-pressure line 12 in thevicinity of the intake side of the compressor 3 and a relief valve 14located at the bypass pixels 13 which releases the high-pressure coolantinto the low-pressure line 12 when the high pressure in thehigh-pressure line 11 reaches a level equal to or higher than a firstspecific value (e.g., 16˜18 MPa) are provided to constitute a firstmeans for safety. With the high-pressure coolant released into thelow-pressure line 12 when the pressure in the high-pressure line 11reaches a level equal to or higher than the first specific value in thismanner, the high pressure can be lowered. It is to be noted that thehigh-pressure side of the bypass passage 13 is set in the vicinity ofthe outlet side of the compressor 3 in this structure by taking intoconsideration the pressure loss in the high-pressure line 11. In otherwords, it is necessary to minimize the high-pressure side coolant volumein the high-pressure line 11 in order to prevent the balance pressurefrom rising when the vehicle is left in the hot sun. Thus, a certaindegree of pressure difference is bound to occur due to the pressure lossbetween the vicinity of the outlet side of the compressor 3 and thevicinity of the intake side of the expansion device 8. Accordingly, inorder to eliminate problems occurring as a result of an increase in thehigh pressure, the high-pressure side of the bypass passage 13 should beset as close as possible to the outlet side of the compressor 3.

In addition, at a specific position in the high-pressure line 11, arupture disk 15 which ruptures at a second specific pressure (e.g.,18˜20 MPa) higher than the first specific pressure is provided as asecond means for safety. As a result, when the high pressure reaches thelevel of the first specific pressure, the rupture disk 15 ruptures toopen communication between the high-pressure line 11 and the atmosphere,thereby discharging the coolant in the high-pressure line 11 into theatmosphere and thus protecting the various devices in the freezing cycle1 from an abnormally high pressure.

A high pressure detection sensor 17 constituting a third means forsafety is provided in the high-pressure line 11, and the high pressuredetected by the high pressure detection sensor 17 is input to a controlunit 18 where it is compared against a third specific pressure (whichmay be set at, for instance, 2˜4 MPa). If it is decided that thedetected high pressure is equal to or lower than the third specificpressure, the power supply to the electromagnetic clutch 2 is stopped todisconnect the compressor 3 from the engine (not shown) thereby stoppingthe drive of the compressor 3. Thus, since a reduction in the quantityof coolant resulting from a coolant leak or the like can be identifiedas the cause of the high pressure becoming lowered to a level equal toor lower than the third specific pressure, the compressor 3 is stoppedto protect the compressor in such an event.

Furthermore, a rupture disk 16 which ruptures at a fourth specificpressure (approximately 12˜13 MPa) higher than the balance pressure(approximately 10 MPa) is provided in the low-pressure line 12 as afourth means for safety, so that the various devices provided on thelow-pressure line 12 are protected by communicating between thelow-pressure line 12 and the atmosphere and releasing the coolant whosepressure has risen into the atmosphere.

By providing the four means for safety described above in the freezingcycle 1, the safety in the freezing cycle 1 using carbon dioxide as thecoolant is improved.

In the embodiment illustrated in FIG. 2, a safety device 40 achieved byforming the first, second and fourth means for safety as an integratedunit is installed as an integrated part of the compressor 3. In thisembodiment, the safety device 40 is mounted at a rear housing 31 of thecompressor 3, with the rear housing 31 having an outlet space 33, whichcommunicates with an outlet hole 32 communicating with a compressionspace (not shown) of the compressor when an outlet valve 34 is opened,formed therein. In the rear housing 31, an intake space 37 communicatingwith an intake hole 36 which communicates with the compression space isalso formed. The outlet space 33 communicates with the gas cooler 4 viaan outlet hole (not shown) and the intake space 37 communicates with thesecond heat exchanging unit 7 of the internal heat exchanger 5 via anintake hole (not shown). In addition, a high-pressure side bypasspassage 38 a and a low-pressure side bypass passage 38 b constitutingthe bypass passage 13 are provided at the rear housing 31, with thesafety device 40 mounted between the high-pressure side bypass passage38 a and the low-pressure side bypass passage 38 b.

The safety device 40 is mounted so as to block off a low-pressure sidespace 39 formed at one end of the low-pressure side bypass passage 38 b,and is provided with a valve seat plate 41 having two through holes 42and 53 communicating with the low-pressure side space 39. In addition, avalve seat 44 is formed at one end of the through hole 53 at the valveseat plate 41. It is to be noted that reference number 43 indicates anO-ring which seals the circumferential edge of the valve seat plate 41.

At a valve housing 50 having a high-pressure space 51 one side of whichis blocked off by the valve seat plate 41, a communicating hole 52communicating between the high-pressure space 51 and the high-pressureside bypass passage 38 a and a high-pressure side release hole 53communicating between the high-pressure space 51 and the atmosphere areformed. At the valve housing, which defines the high-pressure space 51,a low-pressure side release hole 54 communicating with the through hole42 at the valve seat plate 41 is formed.

In the high-pressure space 51, a valve element 45, which closes thethrough hole 53 when it is seated on the valve seat 44, is provided andthe valve element 45 is connected with a bellows 47 via a rod 46. Thebellows 47 is constituted of a plate portion 47A which is linked to therod 46 and holds a spring 49 that applies a force to the valve element45 toward the valve seat via the rod 46 and a retractable bellowsportion 47B that defines an internal space 48 into which a gas achievinga specific pressure level is sealed. When the high pressure within thehigh-pressure space 51 reaches a level equal to or higher than the firstspecific pressure, i.e., when the high pressure becomes larger than theresultant force that includes the force applied by the spring 49 and thepressure of the gas sealed in the bellows 47, the bellows portion 47Bbecomes contracted, causing the valve element 45 to depart from thevalve seat 44, thereby allowing the high-pressure side bypass passage 38a and the low-pressure side bypass passage 38 b to communicate with eachother. Thus, the relief valve 14 functions as the first means forsafety.

In addition, at the front end of the high-pressure side release hole 53,the high-pressure side rupture disk 15, which ruptures at the secondspecific pressure, is provided as the second means for safety. In thehigh-pressure side rupture disk 15, which is constituted of a diskportion 62 that ruptures at the second specific pressure, a retainingportion 61 that holds the disk portion and a screw portion 63 thatsecures the retaining portion 61, the disk portion 62 ruptures to setthe high-pressure side release hole 53 and the atmosphere in acommunicating state when the high pressure in the high-pressure space 51reaches a level equal to or higher than the second specific pressure.

At the front end of the low-pressure side release hole 54, thelow-pressure side rupture disk 16, which ruptures at the fourth specificpressure is provided as the fourth means for safety. In the low-pressureside rupture disk 16, which is constituted of a disk portion 66 thatruptures at the fourth specific pressure, a retaining portion 65 thatholds the disk portion 66 and a screw portion 67 that secures theretaining portion 65, the disk portion 66 ruptures to set thelow-pressure side release hole 54 and the atmosphere in thecommunicating state when the low-pressure in the low-pressure side space39 reaches a level equal to or higher than the fourth specific pressure.It is to be noted that reference number 55 indicates an O-ring thatseals the space between the valve housing and the rear housing 31.

FIG. 3 presents a variation of the embodiment shown in FIG. 2. In thissafety device 70, which is mounted at the rear housing 31 of thecompressor as is the safety device in the previous embodiment, a valveblock 71 is provided to be mounted at the rear housing 31. In the valveblock 71, a high-pressure side passage 72 that is to communicate withthe high-pressure side bypass passage described earlier and alow-pressure side passage 73 to communicate with the low-pressure sidebypass passage are formed, with a valve seat 77 formed at an end on theinside of the low-pressure side passage 73. Furthermore, a high-pressureside release passage 72 a and a low-pressure side release passage 74 areformed at the valve block 71.

One end of the valve block 71 is blocked off by a diaphragm 79, therebydefining a high-pressure space 75. In the high-pressure space 75, avalve element 76 which blocks off the low-pressure side passage 73 whenit is seated on the valve seat 77, is provided, with the valve element76 linked with the diaphragm 79 via a rod 78. The circumferential edgeof the diaphragm 79 is clamped and secured by a case 82 defining a rearchamber space 81 located rearward relative to the diaphragm 79 and alsoby the valve block 71. A spring 80 which applies a force to the valveelement 76 toward the valve seat 77 via the diaphragm 79 and the rod 78is provided in the rear chamber space 81. In addition, a gas at aspecific pressure level is sealed into the rear chamber space 81 as inthe previous embodiment. Thus, a relief valve fulfilling a function asthe first means for safety is achieved.

At the front end of the high-pressure side release passage 72 a, thehigh-pressure side rupture disk 15 is provided as in the previousembodiment, whereas the low-pressure side rupture disk 16 is provided atthe front end of the low-pressure side release passage 74 as in theprevious embodiment. By adopting the structure described above,advantages similar to those achieved in the previous embodiment arerealized.

Furthermore, in the freezing cycle 1 assuming the structure describedabove, a splash-preventing film is formed through coating, spraying ordeposition over areas such as the tank portions of the gas cooler 4, themain unit of the accumulator 10, the tank portions at the evaporator 9,the oil separator main unit which is not shown in FIG. 1 but may beprovided as necessary and the linking areas, as another means forsafety.

The splash-preventing film shown in FIG. 4(a) is constituted by using asa base member 90 preferably PET (polyethylene terephthalate) or PVB(polyvinyl butyryl), i.e., a resin such as a polyethylene resin, apolypropylene resin, a polyvinyl chloride risen or a polyester resin andthen forming an adhesive layer 91 on the surface of the base member 90.The splash-preventing film shown in FIG. 4(b) is constituted as alaminated sheet by enclosing a fibrous substance constituted of resin ormental as a reinforcement layer 92 in the base member 90 (between thebase members 90 a and 90 b) constituting the splash-preventing filmdescribed above.

By providing this means for safety, any splashing resulting fromruptured parts can be prevented even when a rapid fluctuation in thepressure occurs in an unexpected event such as an accident.

Industrial Applicability

As described above, the freezing cycle according to the presentinvention, provided with the first means for safety that leaks highpressure into the low-pressure side when the high pressure reaches alevel equal to or higher than the first specific pressure, the secondmeans for safety that releases the high pressure into the atmospherewhen the high pressure reaches a level equal to or higher than thesecond specific pressure, the third means for safety that stops theoperation of the compressor when the high pressure reaches a level equalto or lower than the third specific pressure and the fourth means forsafety that releases the low-level pressure into the atmosphere when thelow-pressure reaches a level equal to or higher than a specificpressure, improves the safety of the freezing cycle using carbon dioxideas the coolant. As a result, the freezing cycle using carbon dioxide asthe coolant as an alternative to a freon coolant can be employed in anair-conditioning system for vehicles with peace of mind.

Moreover, by forming a splash-preventing film over areas where a ruptureis likely to occur when the pressure in the freezing cycle fluctuates toan abnormal level, the safety level can be further improved.

What is claimed is:
 1. A freezing cycle that uses carbon dioxide as acoolant, comprising, at least: a compressor that compresses the coolantto a super critical range; a radiator that cools the compressed coolant;an expansion device that lowers the pressure of the cooled coolant downto a gas/liquid mixed range; and an evaporator that evaporates aliquid-phase coolant generated by said expansion device, and also havinga high-pressure line extending from an outlet side of said compressor toan intake side of said expansion device and a low-pressure lineextending from an outlet side of said expansion valve to an intake sideof said compressor, characterized by providing with; a first means forsafety that communicates between said high-pressure line and saidlow-pressure line when the pressure in said high-pressure line becomesequal to or higher than a first specific pressure; a second means forsafety that communicates between said high-pressure line and theatmosphere when the pressure in said high-pressure line becomes equal toor higher than a second specific pressure higher than the first specificpressure; a third means for safety that stops the drive of saidcompressor when the pressure in said high-pressure line becomes equal toor lower than a third specific pressure; and a fourth means for safetythat communicates between said low-pressure line and the atmosphere whenthe pressure in said low-pressure line becomes equal to or higher than afourth specific pressure, higher than the third specific pressure.
 2. Afreezing cycle according to claim 1, characterized in that; said firstmeans for safety is constituted of a high-pressure relief valve thatreleases the high pressure to the low-pressure side when the highpressure becomes equal to the first specific pressure.
 3. A freezingcycle according to claim 2, characterized in that; said high-pressurerelief valve communicates between the vicinity of the outlet side ofsaid compressor and the vicinity of the intake side of said compressor.4. A freezing cycle according to claim 3, characterized in that; saidsecond means for safety is constituted of a high-pressure side rupturedisk that ruptures at the second specific pressure higher than the firstspecific pressure.
 5. A freezing cycle according to claim 3,characterized in that; said third means for safety stops said compressorwhen the pressure in said high-pressure line reaches a level equal to orlower than the third specific pressure.
 6. A freezing cycle according toclaim 3, characterized in that; said fourth means for safety isconstituted of a low-pressure side rupture disk that ruptures when thepressure in said low-pressure line becomes equal to the fourth specificpressure higher than the third specific pressure.
 7. A freezing cycleaccording to claim 3, characterized in that; a safety device having anintegrated unit that includes a relief valve constituting said firstmeans for safety, a high-pressure side rupture disk constituting saidsecond means for safety and a low-pressure side rupture diskconstituting said fourth means for safety is created and said safetydevice is installed as an integrated part of said compressor.
 8. Afreezing cycle according to claim 3, characterized in that; asplash-preventing film is formed at said radiator, said accumulators andsaid evaporator.
 9. A freezing cycle according to claim 2, characterizedin that; a safety device having an integrated unit that includes arelief valve constituting said first means for safety, a high-pressureside rupture disk constituting said second means for safety and alow-pressure side rupture disk constituting said fourth means for safetyis created and said safety device is installed as an integrated part ofsaid compressor.
 10. A freezing cycle according to claim 9,characterized in that; a splash-preventing film is formed at saidradiator, said accumulators and said evaporator.
 11. A freezing cycleaccording to claim 2, characterized in that; said second means forsafety is constituted of a high-pressure side rupture disk that rupturesat the second specific pressure higher than the first specific pressure.12. A freezing cycle according to claim 2, characterized in that; saidthird means for safety stops said compressor when the pressure in saidhigh-pressure line reaches a level equal to or lower than the thirdspecific pressure.
 13. A freezing cycle according to claim 2,characterized in that; said fourth means for safety is constituted of alow-pressure side rupture disk that ruptures when the pressure in saidlow-pressure line becomes equal to the fourth specific pressure higherthan the third specific pressure.
 14. A freezing cycle according toclaim 2, characterized in that; a splash-preventing film is formed atsaid radiator, said accumulators and said evaporator.
 15. A freezingcycle according to claim 1, characterized in that; said second means forsafety is constituted of a high-pressure side rupture disk that rupturesat the second specific pressure higher than the first specific pressure.16. A freezing cycle according to claim 15, characterized in that; saidthird means for safety stops said compressor when the pressure in saidhigh-pressure line reaches a level equal to or lower than the thirdspecific pressure.
 17. A freezing cycle according to claim 15,characterized in that; said fourth means for safety is constituted of alow-pressure side rupture disk that ruptures when the pressure in saidlow-pressure line becomes equal to the fourth specific pressure higherthan the third specific pressure.
 18. A freezing cycle according toclaim 15, characterized in that, a safety device having an integratedunit that includes a relief valve constituting said first means forsafety, a high-pressure side rupture disk constituting said second meansfor safety and a low-pressure side rupture disk constituting said fourthmeans for safety is created and said safety device is installed as anintegrated part of said compressor.
 19. A freezing cycle according toclaim 15, characterized in that; a splash-preventing film is formed atsaid radiator, said accumulators and said evaporator.
 20. A freezingcycle according to any of claim 1, characterized in that; said thirdmeans for safety stops said compressor when the pressure in saidhigh-pressure line reaches a level equal to or lower than the thirdspecific pressure.
 21. A freezing cycle according to claim 20,characterized in that; said fourth means for safety is constituted of alow-pressure side rupture disk that ruptures when the pressure in saidlow-pressure line becomes equal to the fourth specific pressure higherthan the third specific pressure.
 22. A freezing cycle according toclaim 20, characterized in that; a safety device having an integratedunit that includes a relief valve constituting said first means forsafety, a high-pressure side rupture disk constituting said second meansfor safety and a low-pressure side rupture disk constituting said fourthmeans for safety is created and said safety device is installed as anintegrated part of said compressor.
 23. A freezing cycle according toclaim 20, characterized in that; a splash-preventing film is formed atsaid radiator, said accumulators and said evaporator.
 24. A freezingcycle according to claim 1, characterized in that; said fourth means forsafety is constituted of a low-pressure side rupture disk that ruptureswhen the pressure in said low-pressure line becomes equal to the fourthspecific pressure higher than the third specific pressure.
 25. Afreezing cycle according to claim 24, characterized in that; a safetydevice having an integrated unit that includes a relief valveconstituting said first means for safety, a high-pressure side rupturedisk constituting said second means for safety and a low-pressure siderupture disk constituting said fourth means for safety is created andsaid safety device is installed as an integrated part of saidcompressor.
 26. A freezing cycle according to claim 24, characterized inthat; a splash-preventing film is formed at said radiator, saidaccumulators and said evaporator.
 27. A freezing cycle according toclaim 1, characterized in that; a splash-preventing film is formed atsaid radiator, said accumulators and said evaporator.
 28. A freezingcycle according to claim 27, characterized in that; saidsplash-preventing film is constituted by using PET (polyethyleneterephthalate) as a base member and forming an adhesive layer at asurface of said base member.
 29. A freezing cycle according to claim 28,characterized in that; said splash-preventing film is constituted as alaminated sheet by enclosing a fibrous substance in said base member.30. A freezing cycle according to claim 27, characterized in that; saidsplash-preventing film is constituted by using PVB (polyvinyl butyryl)as a base member and forming an adhesive layer at a surface of said basemember.
 31. A freezing cycle according to claim 30, characterized inthat; said splash-preventing film is constituted as a laminated sheet byenclosing a fibrous substance in said base member.
 32. A freezing cycleaccording to claim 27, characterized in that; said splash-preventingfilm is constituted as a laminated sheet by enclosing a fibroussubstance in said base member.